<volist name="field.opt" id="option">
    <div class="radio">
        <php>
            $checked = $field['value']==$key ? 'checked' : '';
            $inputId = "id_$field[name]_$key";
        </php>
        <label for="{$inputId}"> <input id="{$inputId}" name="{$field.name}" value="{$key}" type="radio"
                                        {$checked}/>
            {$option}</label> &nbsp;&nbsp;&nbsp;&nbsp;
    </div>
</volist>